从表中删除重复记录

Question

我在MySQL中有一个名为ZipCode的表，它的字段是：id，zipcode，city，state。它有一些重复的记录;一些邮编显示两次 我想删除所有即将到来的邮编，每个邮政编码只能存储一次。 我如何使它正确？

Answer 1

这组三个查询将删除所有重复：

CREATE TABLE new_table AS SELECT * FROM old_table WHERE 1 GROUP BY zip; 
DROP TABLE old_table; 
RENAME TABLE new_table TO old_table; 

Answer 2

-- remove duplicates 

DELETE z1 
FROM ZipCode z1, ZipCode z2 
WHERE z1.zipcode = z2.zipcode AND z2.id < z1.id; 

-- add a primary key 

ALTER TABLE ZipCode ADD PRIMARY KEY (zipcode); 

-- or a unique key 

ALTER TABLE ZipCode ADD UNIQUE INDEX zipcode_unique (zipcode); 

Answer 3

试试这个它的做工精细

DELETE 
FROM 
insurance_policy_customers ipc 
WHERE 
ipc.id NOT IN (SELECT 
min(ipc.id) 
FROM 
insurance_policy_customers ipc 
GROUP BY 
ipc.resident_insurance_policy_id)